Check if Array sum can be made equal to X using K triplet increment operations

Given an array arr of length N and two integers K and X. For every element arr_iin the array, if arr_i > 0 then the elements which are adjacent to it and the element itself will get incremented by 2  for all 1≤i≤N. Check if the sum of all array elements after performing the K operation is equal to X or not.

Examples:

Input: arr[] = { 0, 0, 1, 0, 0, 3 }, K = 2, X = 36
Output: True
Explanation: Initially arr[ ] = { 0, 0, 1, 0, 0, 3 }
After one operation array will be arr [ ] = { 0, 2, 3, 4, 4, 5 }
after Second times array will be arr [ ] = { 2, 4, 7, 8, 8, 7 }
Thus, sum of array is 36 which is equal to X 

Input: arr[ ] = {10, 6, 12, 8, 10, 8}, K = 2, X = 25 
Output: False

Approach: This problem can be solved using brute force hit and trial technique:

• Traverse the given array
• For every index, increment the value at that index and its adjacent index by 2, except for the first and last element because they have only one element adjacent to them.
• Repeat the operations for every possibility in given array till array sum becomes at most X
• If after K operations, in any possibility, the array sum becomes X, return true.
• Else return false, if no such possibility exists.

Below is the implementation of the above approach: 

C++

// C++ program to check whether sum
// Is equal to target value
// After K operations
#include <bits/stdc++.h>
using namespace std;

// Function to check sum of array
// Value is equal to Target
bool find(int arr[], int N, int K, int Target)
{
    while (K--) {
        for (int i = 0; i < N; i++) {
            // If it is first element just increment
            // next element
            if (arr[i] > 0 && i == 0) {
                arr[i + 1] = arr[i + 1] + 2;
            }
            // If it is last element just increment
            // Last second element
            else if (arr[i] > 0 && i == N - 1) {
                arr[N - 2] = arr[N - 2] + 2;
            }
            // If it is not a first element
            // Or not a last element
            // Increment both adjacent value by 2

            else if (arr[i] > 0) {
                arr[i - 1] = arr[i - 1] + 2;
                arr[i + 1] = arr[i + 1] + 2;
            }
        }
    }
    // Calculate sum after performing
    // k times operation
    int ans = accumulate(arr, arr + N, 0);
    if (ans == Target) {
        return 1;
    }
    else {
        return 0;
    }
}
// Driver Code
int main()
{
    int arr[] = { 0, 0, 1, 0, 0, 3 };

    int N = sizeof(arr) / sizeof(arr[0]);
    int K = 2;
    int Target = 36;

    // function call
    cout << (find(arr, N, K, Target)
                 ? "true"
                 : "false");
    return 0;
}

Java

// JAVA program to check whether sum
// Is equal to target value
// After K operations
import java.util.*;
class GFG
{

  // Function to check sum of array
  // Value is equal to Target
  public static boolean find(int arr[], int N, int K,
                             int Target)
  {
    while ((K--) != 0) {
      for (int i = 0; i < N; i++)
      {

        // If it is first element just increment
        // next element
        if (arr[i] > 0 && i == 0) {
          arr[i + 1] = arr[i + 1] + 2;
        }

        // If it is last element just increment
        // Last second element
        else if (arr[i] > 0 && i == N - 1) {
          arr[N - 2] = arr[N - 2] + 2;
        }

        // If it is not a first element
        // Or not a last element
        // Increment both adjacent value by 2
        else if (arr[i] > 0) {
          arr[i - 1] = arr[i - 1] + 2;
          arr[i + 1] = arr[i + 1] + 2;
        }
      }
    }

    // Calculate sum after performing
    // k times operation
    int ans = 0;
    for (int i = 0; i < arr.length; i++) {
      ans += arr[i];
    }

    if (ans == Target) {
      return true;
    }
    else {
      return false;
    }
  }

  // Driver Code
  public static void main(String[] args)
  {
    int arr[] = new int[] { 0, 0, 1, 0, 0, 3 };

    int N = arr.length;
    int K = 2;
    int Target = 36;

    // function call
    System.out.print(
      (find(arr, N, K, Target) ? "true" : "false"));
  }
}

// This code is contributed by Taranpreet

Python3

# Function to check sum of array
# Value is equal to Target
def find(arr, N, K, Target) :

    for j in range(K, 1, -1):
        for i in range(0, N):
            # If it is first element just increment
            # next element
            if (arr[i] > 0 and i == 0) :
                arr[i + 1] = arr[i + 1] + 2

            # If it is last element just increment
            # Last second element
            elif (arr[i] > 0 and i == N - 1) :
                arr[N - 2] = arr[N - 2] + 2

            # If it is not a first element
            # Or not a last element
            # Increment both adjacent value by 2

            elif (arr[i] > 0) :
                arr[i - 1] = arr[i - 1] + 2
                arr[i + 1] = arr[i + 1] + 2



    # Calculate sum after performing
    # k times operation
    ans = 0
    for i in range(0, len(arr)):
        ans += arr[i]

    if (ans == Target) :
        return 1

    else :
        return 0

# Driver Code
arr = [ 0, 0, 1, 0, 0, 3 ]

N = len(arr)
K = 2
Target = 36

# function call
print ( "false" if find(arr, N, K, Target) else "true" )

# This code is contributed by sanjoy_62.

C#

// C# program to check whether sum
// Is equal to target value
// After K operations
using System;

public class GFG{

  // Function to check sum of array
  // Value is equal to Target
  static bool find(int[] arr, int N, int K,
                   int Target)
  {
    while ((K--) != 0) {
      for (int i = 0; i < N; i++)
      {

        // If it is first element just increment
        // next element
        if (arr[i] > 0 && i == 0) {
          arr[i + 1] = arr[i + 1] + 2;
        }

        // If it is last element just increment
        // Last second element
        else if (arr[i] > 0 && i == N - 1) {
          arr[N - 2] = arr[N - 2] + 2;
        }

        // If it is not a first element
        // Or not a last element
        // Increment both adjacent value by 2
        else if (arr[i] > 0) {
          arr[i - 1] = arr[i - 1] + 2;
          arr[i + 1] = arr[i + 1] + 2;
        }
      }
    }

    // Calculate sum after performing
    // k times operation
    int ans = 0;
    for (int i = 0; i < arr.Length; i++) {
      ans += arr[i];
    }

    if (ans == Target) {
      return true;
    }
    else {
      return false;
    }
  }

  // Driver Code
  static public void Main (){

    int[] arr = { 0, 0, 1, 0, 0, 3 };

    int N = arr.Length;
    int K = 2;
    int Target = 36;

    // function call
    Console.Write(
      (find(arr, N, K, Target) ? "true" : "false"));
  }
}

// This code is contributed by hrithikgarg03188.

Javascript

<script>
    // JavaScript program to check whether sum
    // Is equal to target value
    // After K operations

    // Function to check sum of array
    // Value is equal to Target
    const find = (arr, N, K, Target) => {
        while (K--) {
            for (let i = 0; i < N; i++) {
                // If it is first element just increment
                // next element
                if (arr[i] > 0 && i == 0) {
                    arr[i + 1] = arr[i + 1] + 2;
                }
                // If it is last element just increment
                // Last second element
                else if (arr[i] > 0 && i == N - 1) {
                    arr[N - 2] = arr[N - 2] + 2;
                }
                // If it is not a first element
                // Or not a last element
                // Increment both adjacent value by 2

                else if (arr[i] > 0) {
                    arr[i - 1] = arr[i - 1] + 2;
                    arr[i + 1] = arr[i + 1] + 2;
                }
            }
        }
        // Calculate sum after performing
        // k times operation
        let ans = 0;
        for (let indx in arr) {
            ans += arr[indx];
        }
        // accumulate(arr, arr + N, 0);
        if (ans == Target) {
            return 1;
        }
        else {
            return 0;
        }
    }
    // Driver Code

    let arr = [0, 0, 1, 0, 0, 3];

    let N = arr.length;
    let K = 2;
    let Target = 36;

    // function call
    (find(arr, N, K, Target)
        ? document.write("true")
        : document.write("false"));

// This code is contributed by rakeshsahni


</script>

Output

true

Time Complexity: O(N * K)
Auxiliary Space: O(1)